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  • 151.
    Grabbe, Mårten
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Hydro-Kinetic Energy Conversion: Resource and Technology2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The kinetic energy present in tidal currents and other water courses has long been appreciated as a vast resource of renewable energy. The work presented in this doctoral thesis is devoted to both the characteristics of the hydro-kinetic resource and the technology for energy conversion.

    An assessment of the tidal energy resource in Norwegian waters has been carried out based on available data in pilot books. More than 100 sites have been identified as interesting with a total estimated theoretical resource—i.e. the kinetic energy in the undisturbed flow—in the range of 17 TWh. A second study was performed to analyse the velocity distributions presented by tidal currents, regulated rivers and unregulated rivers. The focus is on the possible degree of utilization (or capacity factor), the fraction of converted energy and the ratio of maximum to rated velocity, all of which are believed to be important characteristics of the resource affecting the economic viability of a hydro-kinetic energy converter.

    The concept for hydro-kinetic energy conversion studied in this thesis comprises a vertical axis turbine coupled to a directly driven permanent magnet generator. One such cable wound laboratory generator has been constructed and an experimental setup for deployment in the river Dalälven has been finalized as part of this thesis work. It has been shown, through simulations and experiments, that the generator design at hand can meet the system requirements in the expected range of operation. Experience from winding the prototype generators suggests that improvements of the stator slot geometry can be implemented and, according to simulations, decrease the stator weight by 11% and decrease the load angle by 17%. The decrease in load angle opens the possibility to reduce the amount of permanent magnetic material in the design.

    Delarbeid
    1. A review of the tidal current energy resource in Norway
    Åpne denne publikasjonen i ny fane eller vindu >>A review of the tidal current energy resource in Norway
    2009 (engelsk)Inngår i: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 13, nr 8, s. 1898-1909Artikkel, forskningsoversikt (Fagfellevurdert) Published
    Abstract [en]

    As interest in renewable energy sources is steadily on the rise, tidal current energy is receiving more and more attention from politicans, industrialists, and academics. In this article, the conditions for and potential of tidal currents as an energy resource in Norway are reviewed. There having been a relatively small amount of academic work published in this particular field, closely related topics such as the energy situation in Norway in general, the oceanography of the Norwegian coastline, and numerical models of tidal currents in Norwegian waters are also examined. Two published tidal energy resource assessments are reviewed and compared to a desktop study made specifically for this review based on available data in pilot books. The argument is made that tidal current energy ought to be an important option for Norway in terms of renewable energy.

    sted, utgiver, år, opplag, sider
    Elsevier, 2009
    Emneord
    Tidal current, Renewable energy, Ocean energy
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-113144 (URN)10.1016/j.rser.2009.01.026 (DOI)000269135000012 ()1364-0321 (ISBN)
    Tilgjengelig fra: 2010-10-28 Laget: 2010-01-25 Sist oppdatert: 2018-01-12bibliografisk kontrollert
    2. On the velocity distribution for hydro-kinetic energy conversion from tidal currents and rivers
    Åpne denne publikasjonen i ny fane eller vindu >>On the velocity distribution for hydro-kinetic energy conversion from tidal currents and rivers
    2013 (engelsk)Inngår i: Journal of Renewable and Sustainable Energy, ISSN 1941-7012, E-ISSN 1941-7012, Vol. 5, nr 2, s. 023115-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Tidal currents and rivers are promising sources of renewable energy given that suitable turbines for kinetic energy conversion are developed. To be economically and technically feasible, a velocity distribution that can give a high degree of utilization (or capacity factor), while the ratio of maximum to rated velocity is low would be preferable. The rated velocity is defined as the velocity at which rated power is achieved. Despite many attempts to estimate the resource, however, reports on the possible degree of utilisation from tidal currents and rivers are scarce.

    In this paper the velocity distribution from a number of regulated rivers, unregulated rivers and tidal currents have been analysed regarding the degree of utilisation, the fraction of converted energy and the ratio of maximum to rated velocity. Two methods have been used for choosing the rated velocity; one aiming at a high fraction of converted energy and one aiming at a high degree of utilisation.

    Using the first method, with a rated velocity close to the maximum velocity, it is unlikely that the turbine will reach the cut-out velocity. This results in, on average, a degree of utilisation of 23% for regulated rivers, 19% for unregulated rivers and 17% for tidal currents while converting roughly 30-40% of the kinetic energy. Choosing a rated velocity closer to the mean velocity resulted in, on average, a degree of utilisation of 57% for regulated rivers, 52% for unregulated rivers and 45% for tidal currents. The ratio of maximum to rated velocity would still be no higher than 2.0 for regulated rivers, 1.2 for unregulated rivers and 1.6 for tidal currents. This implies that the velocity distribution of both rivers and tidal currents is promising for kinetic energy conversion. These results, however, do not include weather related effects or extreme velocities such as the 50-year velocity. A velocity factor is introduced to describe what degree of utilisation can be expected at a site. The velocity factor is defined as the ratio U-max/U-rate at the desired degree of utilisation, and serves as an early indicator of the suitability of a site. 

    sted, utgiver, år, opplag, sider
    American Institute of Physics (AIP), 2013
    Emneord
    tidal currents, rivers, degree of utilisation, marine current energy, capacity factor, renewable energy, velocity factor
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-195499 (URN)10.1063/1.4795398 (DOI)000318242100037 ()
    Tilgjengelig fra: 2013-04-12 Laget: 2013-02-25 Sist oppdatert: 2017-12-06bibliografisk kontrollert
    3. A low-speed generator for energy conversion from marine currents: experimental validation of simulation
    Åpne denne publikasjonen i ny fane eller vindu >>A low-speed generator for energy conversion from marine currents: experimental validation of simulation
    2008 (engelsk)Inngår i: Proceedings of the Institution of mechanical engineers. Part A, journal of power and energy, ISSN 0957-6509, E-ISSN 2041-2967, Vol. 222, nr 4, s. 381-388Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A low-speed permanent magnet (PM) cable wound generator for electrical energy conversion from marine or tidal currents has been designed and constructed. A key feature of this variable speed direct drive generator is its capability to efficiently generate electricity from tidal currents with very low velocities, in the order of 1 m/s. In arriving at an appropriate design for the generator typical characteristics of tidal currents were considered. Using these characteristics as input, and accounting for the electromagnetic losses, detailed computer simulations using a finite-element method software were carried out to come up with the final design. Various parameters that can influence the generator design are presented. An experimental set-up has been constructed based on the above-mentioned design in order to study the electrical and mechanical performance of the generator through a variety of experiments. The power input for this set-up is a variable speed motor, capable of operating the generator at rotational speeds of 0–16 r/min, representing tidal currents with very low velocities. The generator presented in this paper may be beneficial for a better understanding of an appropriate design and layout of tidal energy conversion systems.

    Emneord
    finite-element method, marine currents, permanent magnet generator, tidal power
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-96614 (URN)10.1243/09576509JPE567 (DOI)000258167400005 ()
    Tilgjengelig fra: 2008-01-11 Laget: 2008-01-11 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    4. Matching a permanent magnet synchronous generator to a fixed pitch vertical axis turbine for marine current energy conversion
    Åpne denne publikasjonen i ny fane eller vindu >>Matching a permanent magnet synchronous generator to a fixed pitch vertical axis turbine for marine current energy conversion
    Vise andre…
    2009 (engelsk)Inngår i: IEEE Journal of Oceanic Engineering, ISSN 0364-9059, E-ISSN 1558-1691, Vol. 34, nr 1, s. 24-31Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Extracting energy from a free-flow marine current using a vertical axis fixed pitch turbine requires a generator that can handle varying speeds and loads, since such a turbine gives maximum power capture for a fixed tip speed ratio. A prototype of such a generator has been designed and constructed. In this paper, its variable speed and load operation is evaluated, both in terms of how the constructed generator performs in relation to simulations, and in terms of how the generator could perform with three different fixed pitch turbines. Measurements of root mean square (RMS) voltage and current differ 10% from simulations. Performance analysis with example turbines shows that the generator can match fixed tip speed ratio operation of several turbines for current speeds between 0.5 and 2.5 m/s.

    Emneord
    Fixed tip speed ratio operation, permanent magnet generators, tidal power generation, variable speed generator, vertical axis turbine
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-96617 (URN)10.1109/JOE.2008.2010658 (DOI)000264618000003 ()
    Tilgjengelig fra: 2008-01-11 Laget: 2008-01-11 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    5. A Permanent Magnet Generator for Energy Conversion from Marine Currents: No Load and Load Experiments
    Åpne denne publikasjonen i ny fane eller vindu >>A Permanent Magnet Generator for Energy Conversion from Marine Currents: No Load and Load Experiments
    2012 (engelsk)Inngår i: ISNR Renewable Energy, ISSN 2090-7451, Vol. 2012, s. 489379-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    This paper presents experiments and measurements on a low speed permanent magnet cable wound generator for marine currentenergy conversion.Measurements were made for no load and nominal load (4.44Ω/phase) conditions at nominal speed (10 rpm).For either load condition, the magnetic fields in the air gap were also measured. The measurements on the generator werecompared with the corresponding finite element method simulations used to design the machine. It is shown in the paper thatmeasurements and corresponding case simulations show good agreement. At nominal speed, the measured and simulated loadvoltages (nominal load) differ less than 1% for the rms values and less than 5% for peak values. At no load, measured and simulatedvoltages had larger differences, that is, <9% for rms values and <5% for peak values. Harmonic analyses of measured and simulatedphase voltages and currents show only the presence of third harmonics. The percentage of harmonics in the measured data wascomparable with the corresponding predictions of the simulations. The discussions and results presented in the paper could bebeneficial for future design of efficient and reliable marine current energy converter systems.

    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-176990 (URN)10.5402/2012/489379 (DOI)
    Tilgjengelig fra: 2012-06-29 Laget: 2012-06-29 Sist oppdatert: 2013-03-22bibliografisk kontrollert
    6. On the Stator Slot Geometry of a Cable Wound Generator for Hydrokinetic Energy Conversion
    Åpne denne publikasjonen i ny fane eller vindu >>On the Stator Slot Geometry of a Cable Wound Generator for Hydrokinetic Energy Conversion
    2015 (engelsk)Inngår i: Scientific World Journal, ISSN 1537-744X, E-ISSN 1537-744X, artikkel-id 812149Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    In this paper, the stator slot geometry of a cable wound permanent magnet synchronous generator for hydro-kinetic energy conversion is evaluated. When designing generators, practical experience is of great importance to result in a realizable design. Therefore, practical experience from winding two cable wound generators is used to propose optimized dimensions of different parts in the stator slot geometry. A thorough investigation is performed through simulations of how small geometrical changes alter the generator performance. Simulations are performed by using the finite element method (FEM) to solve coupled field and circuit equations. The parameter study shows that small changes in the geometry can have large affect on the performance and the generator dimensions. Furthermore, it is concluded that the load angle is especially sensitive to small geometrical changes. A new generator design is proposed which shows improved efficiency, reduced weight and a possibility to decrease the expensive permanent magnet material by almost one fifth.

    Emneord
    permanent magnet, synchronous generator, tidal energy, hydro-kinetic energy conversion, cable wound
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-195501 (URN)10.1155/2015/812149 (DOI)
    Tilgjengelig fra: 2013-02-25 Laget: 2013-02-25 Sist oppdatert: 2017-12-06bibliografisk kontrollert
    7. Design of an experimental setup for hydro-kinetic energy conversion
    Åpne denne publikasjonen i ny fane eller vindu >>Design of an experimental setup for hydro-kinetic energy conversion
    Vise andre…
    2009 (engelsk)Inngår i: International Journal on Hydropower & Dams, ISSN 1352-2523, Vol. 16, nr 5, s. 112-116Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A hydro-kinetic energy project has been underway in Sweden since 2000, and an in-stream prototype setup for experiments at a site in a Swedish river is now in progress. The system comprises a vertical axis turbine and a directly driven permanent magnet generator. Methods and choices used in designing the system are described here. The turbine and generator are evaluated based on measurements and CFD simulations of conditions at the site for the experimental setup.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-113145 (URN)1352-2523 (ISBN)
    Tilgjengelig fra: 2010-01-25 Laget: 2010-01-25 Sist oppdatert: 2016-04-14bibliografisk kontrollert
    8. Efficiency of a Directly Driven Generator for Hydrokinetic Energy Conversion
    Åpne denne publikasjonen i ny fane eller vindu >>Efficiency of a Directly Driven Generator for Hydrokinetic Energy Conversion
    2013 (engelsk)Inngår i: Advances in Mechanical Engineering, ISSN 1687-8132, E-ISSN 1687-8140, s. 978140-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    An experimental setup for hydrokinetic energy conversion comprising a vertical axis turbine, a directly driven permanent magnet generator, and a control system has been designed and constructed for deployment in the river Dalälven in Sweden. This paper is devoted to discussing the mechanical and electrical design of the generator used in the experimental setup. The generator housing is designed to be water tight, and it also acts as a support structure for the turbine shaft. The generator efficiency has been measured in the range of 5–16.7 rpm, showing that operation in the low velocity range up to 1.5 m/s is possible with a directly driven generator.

    Emneord
    permanent magnet, cable wound, tidal energy, ocean energy, generator
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-195876 (URN)10.1155/2013/978140 (DOI)000325895100001 ()
    Tilgjengelig fra: 2013-02-28 Laget: 2013-02-28 Sist oppdatert: 2017-12-06bibliografisk kontrollert
  • 152.
    Grahl, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Energikartläggning av en livsmedelsindustri: samt förslag på energieffektiviserande åtgärder2015Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis concerns an energy audit of a food industry. The company's business consists of boiling and peeling shrimps, and producing mayonnaise-based salads. This type of work involves energy-intensive processes, such as steam generation, compression of air and refrigeration of large spaces. These needs are supplied with electricity. Furthermore, the industry is a major consumer of district heating, particularly for heating the supply air in the ventilation system. The energy-related processes in the operations consume about 2,300 MWh of electricity and 660 MWh of district heating. There are opportunities to improve the efficiency by controlling the processes, merging different parts of the systems , implementing equipment for energy recovery, and installing more energy-efficient equipment. The primary aim of the food industry is to produce high quality food. In this context it is no wonder that matters that do not affect the primary tasks receive a lower priority. There may, however, be good reason to place these energy-related issues higher on the agenda. 

  • 153.
    Grahn, Elin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Industriell teknik.
    Utveckling och tillämpning av modeller förkvantifiering av de ekonomiska konsekvensernaav ökad förbrukningsflexibilitet inom eldistribution2015Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    One step towards a more sustainable energy system is to create a more flexible electrical grid, where increased demand response among electricity consumers can play an important role. A distribution grid owner can encourage their customers to use electricity more evenly distributed during the day by introducing different types of grid fees such as time-differentiated power tariffs. In this master thesis, the theoretical economic impact of a flattened load profile for a distribution grid owner is investigated. Different factors that impact the distribution grid owner’s economy are identified and two are chosen to be quantified; losses in the grid and the fee to the feeding grid. The possibility to save money by avoiding future investments is discussed but not quantified. Models are developed for modifying an existing load profile, calculating the losses associated with a certain grid and load profile, and calculating the value of a lowered subscribed power to the feeding grid. The models are applied on the distribution grid owner Sala-Heby Energi Elnät AB. The results show that with a load profile that is flattened out 100% every day, which is the theoretical best possible scenario, the losses can be reduced with 2.6% which corresponds to a value of 81 000 SEK. By lowering the subscribed power to the feeding grid as much as the highest peak of the year is reduced in the modified load curve, the cost to the feeding grid would be reduced 1.2 million SEK, or 10% of the fee to the feeding grid. In the 20% curve modification case, which would be more realistic to achieve in reality, the losses decreased by 0.9% which corresponds to a value of 29 000 SEK. Furthermore, the fee to feeding grid would be reduced with 0.34 million SEK which corresponds to 2.8% of the total fee. In summary, the theoretical economic saving potential is around 10 times higher for the fee to feeding grid than for grid losses.

  • 154.
    Grandell, Leena
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Globala energisystem.
    Hall, Charles
    State University of New York.
    Höök, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Globala energisystem.
    Energy Return on Investment for Norwegian Oil and Gas from 1991 to 20082011Inngår i: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 3, nr 11, s. 2050-2070Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Norwegian oil and gas fields are relatively new and of high quality, which has led, during recent decades, to very high profitability both financially and in terms of energy production. One useful measure for profitability is Energy Return on Investment, EROI. Our analysis shows that EROI for Norwegian petroleum production ranged from 44:1 in the early 1990s to a maximum of 59:1 in 1996, to about 40:1 in the latter half of the last decade. To compare globally, only very few, if any, resources show such favorable EROI values as those found in the Norwegian oil and gas sector. However, the declining trend in recent years is most likely due to ageing of the fields whereas varying drilling intensity might have a smaller impact on the net energy gain of the fields. We expect the EROI of Norwegian oil and gas production to deteriorate further as the fields become older. More energy-intensive production techniques will gain in importance.

  • 155.
    Granqvist, Claes G.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Recent progress in electrochromics and thermochromics: A brief survey2016Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 614, s. 90-96Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Contemporary architecture is characterized by large glazings, which are able to accomplish good indoors-outdoors contact and daylighting. However, glazings, encompassing windows and glass facades, are challenging with regard to energy efficiency and often lead to excessive solar energy ingress and to large thermal losses, which must be balanced by energy-demanding cooling or heating. Cooling, especially, has grown strongly in importance during recent years. Emerging technologies utilizing thermochromics and electrochromics allow control of the inflow of visible light and solar energy and thereby produce better energy efficiency than traditional glazings employing static solutions. Thermochromic thin films, based on vanadium dioxide, let through less solar energy at high temperature than at low temperature, whereas electrochromic devices include thin films-usually based on tungsten oxide and nickel oxide-that can change their transmittance of solar energy and visible light upon the application of a voltage. It is important that electrochromics, and to some degree thermochromics, can enhance indoor comfort and lead to better living and working conditions. The present brief review covers a number of recent advances in thermochromics and electrochromics with a view to applications in energy-efficient buildings.

  • 156.
    Granqvist, Claes Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    In harmony with the environment: New materials and devices for harnessing nature's energy flows2018Inngår i: Conference Guide, 2018, artikkel-id 1 pageKonferansepaper (Annet vitenskapelig)
  • 157.
    Granqvist, Claes Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    In harmony with the environment: New materials and devices for harnessing nature's energy flows2018Inngår i: Book of Abstracts / [ed] NV Skorodumova, Igor A Pasti, Biljana Sljukic Paunkovic, 2018, artikkel-id 1 pageKonferansepaper (Annet vitenskapelig)
  • 158.
    Granqvist, Claes Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Progress in materials for harnessing nature's energy flows: Something old, something new, something borrowed, something blue2018Inngår i: Abstracts, 2018, s. 15-Konferansepaper (Fagfellevurdert)
  • 159.
    Granqvist, Claes Göran
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Niklasson, Gunnar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Solar energy materials for heating and cooling: Part One2018Inngår i: SVC Society of Vacuum Coaters Bulletin, nr spring issue, s. 36-45Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Solar energy materials have properties that are tailored to the characteristics of the electromagneti cradiation in our natural surroundings, specifically its spectral distribution, angle of incidence, and intensity. This tailoring can be made withregard to solar irradiation, thermal emission, atmospheric absorption, visiblelight, photosynthetic efficienry and more. Solarenergy materials can be of many kinds, e.g., metallic, semiconducting, dielectric, glassy, polymeric, gaseous, etc.

  • 160.
    Granqvist, Claes Göran
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Niklasson, Gunnar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Solar energy materials for heating and cooling: Part Two2018Inngår i: SVC Bulletin, nr summer issue, s. 26-41Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Solar energy materials have properties that are tailored to the characteristics of the electromagnetic radiation in our natural surroundings, specifically its spectral distribution, angle of incidence, and intensity. This tailoring can be made with regard to solar irradiation, thermal emission, atmospheric absorption, visible light, photosynthetic efficiency and more. Solar energy materials can be of many kinds, e.g., metallic, semiconducting, dielectric, glassy, polymeric, gaseous, etc. They can be bulk-like, as outlined in an earlier article in SVC Bulletin, spring issue, pp. 36–45, 2018, and they can be based on thin surface coatings as discussed below. The purpose of both articles is to provide a bird’s eye view over a wide class of materials of rising importance rather than giving detailed accounts of highly specialized topics. The two articles are based on a recent paper in Solar Energy Materials and Solar Cells 180, pp. 213–226, 2018 (with permission from Elsevier).

  • 161.
    Grawé, Matilda
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
    Demand Response in the Engineering Industry: Based on a case study of Volvo Powertrain Production in Köping2017Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The climate change is driving a change in technology and promotes intermittent electricity; solar and wind, and also promotes new technology such as electrical vehicles. The increased share of intermittent  power and changed patterns of using power causes large strain on the powergrids during critical hours of the year. The system The Eergimarknadsinspektionen as well as the European transmission system operators are therefore requesting that electricity users adapt their power consumption to when power is generated. This is rather opposite to the present situation where the TSO’s respond to the customers demand by increasing their power generation. This new change of customers adapting to the current power available is called Demand response (DR).

    The thesis investigates drivers, barriers and potential for demand response within the engineering industry. It is based on interviews with representatives from enginering industries, system operators as well as a case study on Volvo Group Trucks Operations Powertrain Production in Köping. The potential is also determined through a simulation carried out in collaboration with Johan Norberg, a masterstudent at the Royal Technical Highschool.

    The conclusion states that it is possible for Volvo Pwertrain to participate in DR events, however the economical compensation identified in this thesis is not enough.

  • 162.
    Grim, Johanna
    Sveriges lantbruksuniversitet, Fakulteten för naturresurser och jordbruksvetenskap, Institutionen för energi och teknik.
    Energianalys av hygieniseringssystem: jämförelse av befintlig pastörisering med integrerad termofil hygienisering på Kungsängens gårds biogasanläggning i Uppsala2014Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The biogas plant Kungsängens gård, owned by Uppsala Vatten och Avfall AB, produces biogas and biomanure from organic household waste, food processing waste and slaughterhouse waste. In year 2012, 4.4 million Nm3 of biogas were produced from 25 200 tons of waste. Before digestion all substrate is sanitized by pasteurization at 70°C in order to kill pathogens. Another method, integrated thermophilic sanitation (ITS), is of interest in order to decrease the energy demand. The method implies that the substrate is sanitized during ten hours in the digestion chamber, where the temperature is 52°C. The purpose of this thesis was to compare pasteurization with integrated thermophilic sanitation from an energy point of view. The pasteurization´s impact on biogas production and energy yield was examined through experiments with two laboratory digesters, of which one was fed with pasteurized substrate and the other with non-pasteurized substrate. For the present pasteurization system, electricity and heat demand was surveyed. For the integrated thermophilic sanitation, a process design was developed and dimensioned and the electricity and heat demand was calculated. Thereafter, the energy yield and energy demand for the two sanitation systems were compared. The result showed that pasteurization had no effect on biogas production. The energy yield was on average 4.79 kWh/kg VS from non-pasteurized substrate and 4.74 kWh/kg VS from pasteurized substrate. There was no statistically significant difference between the reactors. The energy audit showed that pasteurization required 0.48 kWh/kg VS, which is 85 % of the total energy consumption at the facility. The digester warming demanded 0.077 kWh/kg VS for RK1 and 0.031 kWh/kg VS for RK2. The electricity consumption was 0.041 kWh/kg VS. The process of ITS was designed with a heat exchange from bio manure to substrate, followed by heating to 52°C by steam addition. The heat requirement was 0.24 kWh/kg VS and the electricity demand was 0.034 kWh/kg VS. The warming of the digesters was the same as in the present pasteurization system. The comparison between the existing pasteurization and the ITS showed that switching systems would save 0.243 kWh/kg VS or 46 % of the present energy consumption. This corresponds to annual savings of 1.22 GWh. A sensitivity analysis showed that the results were sensitive to assumptions regarding the heat exchanger in the case of ITS. 10 % energy losses resulted in smaller savings, 34 % or 0.91 GWh per year. There are increased risks of process disruptions if ITS is combined with an increased organic loading rate. 4.2 % reduction of the total biogas production erases the energy savings which means that it is important that process stability is ensured.

  • 163.
    Gueymard, Christian A.
    et al.
    Solar Consulting Serv, Colebrook, NH USA.
    Bright, Jamie M.
    Australian Natl Univ, Fenner Sch Environm & Soc, Canberra, ACT, Australia.
    Lingfors, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Habte, Aron
    Natl Renewable Energy Lab, Golden, CO USA.
    Sengupta, Manajit
    Natl Renewable Energy Lab, Golden, CO USA.
    A posteriori clear-sky identification methods in solar irradiance time series: Review and preliminary validation using sky imagers2019Inngår i: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 109, s. 412-427Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    This study examines all known methods that have been proposed in the literature to identify clear-sky periods in historical solar irradiance time series. Two different types of clear-sky detection (CSD) methods are discussed: those (16 total) that attempt to isolate periods of 1-min or more cloudless conditions, and those (5 total) that only attempt to detect clear-sun periods. All methods are found to rely on a diversity of inputs and on a variety of tests that typically examine the smoothness of the temporal variation of global and/or direct irradiance. Using samples of a few days with variable cloudiness, it is shown that these methods all have obvious strengths and weaknesses. Although this justifies a detailed validation to determine which method(s) could be best suited in the practice of solar radiation modeling or other applications, the current lack of appropriate equipment at high-quality reference radiometric stations prevents such an endeavor. Only a preliminary study is conducted here at seven stations of the SURFRAD network in the U.S., where 1-min irradiance measurements are available, along with sky data from a Total Sky Imager (TSI). The many limitations of the latter prevent its data to be considered "ground truth" here. Nevertheless, the comparison of the results from all CSD methods and 1.2 million TSI observations from all SURFRAD sites provides important qualitative and quantitative information, using a variety of performance indicators. Overall, two CSD methods appear more robust and are recommended, pending better high-resolution and high-performance cloud observations from modern sky cameras to redo these tests.

  • 164.
    Gullberg, Ylva
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Hantering av överskottsel från byggnadsintegrerade solceller: Ekonomiska möjligheter för batterier och värmelager2017Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Renovating roofs of multi-family buildings with building integrated photovoltaics (BIPV) poses a possibility of cost effective installation of solar cells. The surplus electricity could however become a problem for the grid and decrease the profitability of the investment. In this study, the economical possibilities for a BIPV renovation and for batteries and a thermal storage to store the surplus electricity is evaluated.

    A study has been made for a multi-family building in Jönköping which is built within the time period of the Swedish Million Programme. Several cases were examined where the renovation was combined with installation of BIPV, a heat recovery system (HRV) or heat pump and a possibility of batteries and/or thermal storage. The management of surplus electricity was modelled and the net present value (NPV) for the cases as well as the value of energy storage was calculated.

    The NPV was positive for all the cases with BIPV renovation, which means that the BIPV renovation is profitable. The alternative cost for the renovation was seen to have a big impact on the profitability. Both the batteries and the thermal storage decreased the NPV and are therefore not profitable today. To increase the profitability of energy storage the investment cost must decrease and/or the energy prices increase. Other possibilities to increase the profitability of the investment was found; to make use of the different political support systems, or to have a group subscription where also the household electricity can be supplied by the solar production.

  • 165.
    Gultekin, Ahmet
    et al.
    Istanbul Tech Univ, Energy Inst, TR-34469 Istanbul, Turkey.
    Aydin, Murat
    Bochum Univ Appl Sci, Int Geothermal Ctr, D-44801 Bochum, Germany.
    Sisman, Altug
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori. Istanbul Tech Univ, Energy Inst, TR-34469 Istanbul, Turkey.
    Effects of arrangement geometry and number of boreholes on thermal interaction coefficient of multi-borehole heat exchangers2019Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 237, s. 163-170Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In large-scale ground-source heat pump applications, a large number of borehole heat exchangers are used and performance losses become an important issue due to thermal interactions. Dependency of total performance losses on borehole spacing can analytically be expressed by using thermal interaction coefficient. For a given application field, interaction coefficient depends on number of boreholes (N), aspect ratio of borehole's arrangement geometry and operation time. In this study, functional dependencies of interaction coefficient on N and aspect ratio are investigated by considering different rectangular borehole arrangements. Dependencies of both thermal interaction coefficient and total heat transfer rate on aspect ratio are computationally examined. Also, the effects of number of boreholes and operation time on interaction coefficient are studied. The results showed that the values of both interaction coefficient and performance losses decrease with the decrease of aspect ratio of a borehole field. Aspect ratio dependency of total unit heat transfer rate becomes more evident in case of shorter borehole spacing. Furthermore, a strong dependency of interaction coefficient on N is observed when N is much smaller than a critical value, Nc, although an asymptotic behavior appears and dependency on N becomes negligible for N > Nc. Some empiric expressions are proposed for aspect ratio and N dependency of interaction coefficient as well as Nc. The results and the proposed expressions can be used to make an energy efficient and optimal design of a BHE field by maximizing the total performance while minimizing the field allocation and the thermal losses.

  • 166.
    Gustafsson, Johan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten.
    Lågtempererade uppvärmningssystem och dess potential i nybyggda och energieffektiva kontorshus: En studie i att använda returtemperatur från befintlig bebyggelse till uppvärmning2018Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    This master thesis examine how a low temperature radiator systemcan be implemented in a new built office and what effects this will have on the return temperature. One point in the system was logged and data was collected. A model was then developed in VIP-Energy to determine the heating demand for an office building which were compared to the supply. A cost analysis was also performed on different types of low temperature radiator systems. These were compared to a conventional radiator system with a supply temperature of 55°C and a return temperature of 45°C. A cost analysis was also done on whether to build energy efficient or not. The study shows a strong correlation between the heat demand and the time of day. The demand is low during office hours and high during nights and weekends with a peak demand of 70 kW. The low demand is due to the high amount of process energy an office uses. The point in the system can supply the heat demand during almost every hour of the year. For the few hours where there is a mismatch between supplied heat and demand, a shunt solution can supply the return water with primary heat. If the heat demand is scaled up with ten or twenty identical houses the point will be unable to supply enough power to cover the heat demand for more hours a year. The most cost-effective radiator system is Purmo Belize with a supply temperature of 40°C and a return temperature of 30°C. Purmo Belize has built in fans that can improve the heat supply to the room with up to 80 %. Compared to a conventional radiator the payback time is 9 years, with a return on investment of 12,8 percent and a net present value of 151 762 kr. A 40/30°C-system will lower the return temperature in the measured point with 0,4°C. For the whole system this means a reduced temperature of 0,00003°C if the total flow is 50 m3/s and the average return temperature is 50°C. From a strictly economic point of view, an extra energy efficient house will be beneficial if the extra cost is up to 5 000 000 kr or around 700 kr/m2 with a depreciation time of 25 years.

  • 167. Gutland, M.
    et al.
    Bucking, S.
    Santana, M.
    Integrated energy and hygrothermal analyses of heritage masonry structures in cold climates2018Inngår i: Conference Report: The 3rd International Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström, Lisa Nilsen and Susanna Carlsten, Uppsala University, 2018, s. 423-432Konferansepaper (Fagfellevurdert)
  • 168.
    Gårdö, Viktor
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. Tsinghua University.
    Lindholm, Yasmin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. Tsinghua University.
    Safety Analysis of the Baihetan Dam: By Investigating the Pressure Distribution on the Plunge Pool Floor2013Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Baihetan Dam is sited on the lower reaches of the Jinsha River in the southwest of China between the boarders of Sichuan and Yunnan province. The dam is scheduled to be taken into operation in the year of 2020 with an installed generation capacity of 14 GW which will put Baihetan Dam on the map as the third largest hydropower station in the world considering installed power output. In comparison, the world’s biggest dam Three Gorges has an installed generation capacity of 22,5 GW.

    To ensure a sufficient safety evaluation in terms of erosion (scour) formation at the bottom of the plunge pool, pressure simulations in the plunge pool floor in an experimental model at the Department of Hydraulic Engineering in Tsinghua University, Beijing, China has been performed. Data from two experiments with two different outflow configurations has been obtained and analyzed together with three earlier performed experiments on the same experimental model.

    The results from outflow configuration one had an incomplete data set and could not be compared to the other experiments. The results retrieved from the other experiments however showed the importance of a spillway design with nappe splitters and nappe blocks implemented and the value of a sufficient water cushion in the plunge pool. All four outflow configurations with nappe splitters or nappe blocks implemented held a hydrodynamic pressure below the recommended maximum pressure value of 15 cm water head (experimental model scale) stated by the East Asian Investigation and Design Institute, whilst the one configuration with no nappe splitters or nappe blocks exceeded the value. The design of outflow configuration two is four nappe splitters implemented in two spillways and two nappe blocks in two spillways. In this thesis, this configuration has proven to be the most suitable one in terms of maximum pressure minimization and pressure distribution at the plunge pool floor. 

  • 169.
    Göteman, Malin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Wave energy parks with point-absorbers of different dimensions2017Inngår i: Journal of Fluids and Structures, ISSN 0889-9746, E-ISSN 1095-8622, Vol. 74, s. 142-157Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An analytical model for point-absorbing wave energy converters connected to floats of different geometries and topologies is presented. The floats can be truncated cylinder or cylinder with moonpool buoys and have different outer radius, inner radius, draft, mass and can be connected to linear generators of different power take-off constants. The model is implemented into a numerical code where the input is measured time-series of irregular waves. After validation against benchmark software, the model is used to study optimal configurations of wave energy arrays consisting of different wave energy devices. It is shown that the total power absorption can be improved if the wave energy array consists of devices of different dimensions, and that a higher power-to-mass ratio can be achieved.

  • 170.
    Göteman, Malin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Eriksson, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Hann, Martyn
    Ransley, Edward
    Greaves, Deborah
    Leijon, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Wave loads on a point-absorbing wave energy device in extreme waves2015Inngår i: Journal of Ocean and Wind Energy, ISSN 2310-3604, Vol. 2, nr 3, s. 176-181Artikkel i tidsskrift (Fagfellevurdert)
  • 171.
    Göteman, Malin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Eriksson, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Isberg, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Fast modeling of large wave energy farms using interaction distance cut-off2015Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 8, nr 12, s. 13741-13757Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In many wave energy concepts, power output in the MW range requires the simultaneous operation of many wave energy converters. In particular, this is true for small point-absorbers, where a wave energy farm may contain several hundred devices. The total performance of the farm is affected by the hydrodynamic interactions between the individual devices, and reliable tools that can model full farms are needed to study power output and find optimal design parameters. This paper presents a novel method to model the hydrodynamic interactions and power output of very large wave energy farms. The method is based on analytical multiple scattering theory and uses time series of irregular wave amplitudes to compute the instantaneous power of each device. An interaction distance cut-off is introduced to improve the computational cost with acceptable accuracy. As an application of the method, wave energy farms with over 100 devices are studied in the MW range using one month of wave data measured at an off-shore site.

  • 172.
    Göteman, Malin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Eriksson, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Isberg, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Optimizing wave energy parks with over 1000 interacting point-absorbers using an approximate analytical method2015Inngår i: International Journal of Marine Energy, ISSN 2214-1669, Vol. 10, s. 113-126Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Large arrays of wave energy converters of point-absorber type are studied using an approximate analytical model. The model is validated against a numerical method that takes into account full hydrodynamic interactions based on linear potential flow theory. The low computational cost of the analytical model enables parameter studies of parks in the MW range and includes up to over 1000 interacting devices. The model is actuated by irregular wave data obtained at the Swedish west coast. In particular, focus is on comparing park geometries and improving park configurations to minimize the power fluctuations.

  • 173.
    Göteman, Malin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Giassi, Marianna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Isberg, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Advances and Challenges in Wave Energy Park Optimization - A Review2020Inngår i: Frontiers in Energy Research, E-ISSN 2296-598X, Vol. 8, nr 26Artikkel i tidsskrift (Fagfellevurdert)
  • 174.
    Göteman, Malin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Giassi, Marianna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    McNatt, Cameron
    Mocean Energy, Edinburgh, Scotland.
    Wave energy park interactions in short-crested waves2018Konferansepaper (Fagfellevurdert)
  • 175.
    Göteman, Malin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mathew, Jude
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Castellucci, Valeria
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Giassi, Marianna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Waters, Rafael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Wave energy farm performance and availability as functions of weather windows2018Konferansepaper (Fagfellevurdert)
  • 176.
    Göteman, Malin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    McNatt, Cameron
    Mocean Energy, Edinburgh EH9 3BF, Midlothian, Scotland.
    Giassi, Marianna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Isberg, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Arrays of Point-Absorbing Wave Energy Converters in Short-Crested Irregular Waves2018Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, nr 4, artikkel-id 964Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For most wave energy technology concepts, large-scale electricity production and cost-efficiency require that the devices are installed together in parks. The hydrodynamical interactions between the devices will affect the total performance of the park, and the optimization of the park layout and other park design parameters is a topic of active research. Most studies have considered wave energy parks in long-crested, unidirectional waves. However, real ocean waves can be short-crested, with waves propagating simultaneously in several directions, and some studies have indicated that the wave energy park performance might change in short-crested waves. Here, theory for short-crested waves is integrated in an analytical multiple scattering method, and used to evaluate wave energy park performance in irregular, short-crested waves with different number of wave directions and directional spreading parameters. The results show that the energy absorption is comparable to the situation in long-crested waves, but that the power fluctuations are significantly lower.

  • 177. Haas, F.
    et al.
    Herrera, D.
    Hüttler, W.
    Exner, D.
    Troi, A.
    Historic Building Atlas: Sharing best practices to close the gap between research & practice2018Inngår i: Conference Report: The 3rd International Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström, Lisa Nilsen and Susanna Carlsten, Uppsala University, 2018, s. 236-245Konferansepaper (Fagfellevurdert)
  • 178.
    Hagner, Emma
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Nya utmaningar för småskalig vattenkraft: Konsekvensutredning av Vattenverksamhetsutredningens delbetänkande 2013:69.2014Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    I oktober 2013 publicerade Vattenverksamhetsutredningen delbetänkandet SOU 2013:69 med förslag på förnyade vattenrättsliga regler. Förslaget är att genomföra en nyprövning av alla de vattenverksamheter som inte har tillstånd enligt miljöbalken för att på så sätt uppdatera miljökraven i deras äldre tillstånd till dagens nivå. Enligt utredningen är detta nödvändigt för att Sverige ska uppnå de miljömål som satts enligt EU:s ramdirektiv för vatten. Enligt förslaget i delbetänkandet skulle ca 98 % av de svenska vattenkraftverken genomgå en nyprövning och det finns en oro över hur de nya miljökraven kan komma att minska den förnybara energiproduktionen.

    Syftet med detta examensarbete var att utreda vilka konsekvenser den småskaliga vattenkraften står inför om Vattenverksamhetsutredningens förslag skulle bli verklighet. Fokus har lagts på anläggningar med en installerad effekt under 1,5 MW, så kallad minkraft, och tre exempelfall har valts ut och utretts. Det har antagits att de nya miljökraven skulle innebära att anläggningarna ska anlägga fiskpassager, upp- och nedströms, och att de fall där det finns torrlagda åfåror skulle införa en minimitappning av vattendragets medellågvattenföring (MLQ). Inom de tre exempelfallen finns även de tre ägargrupperna privat, kommunal och elbolag representerade av en vardera.

    Kostnader har beräknats för flera olika åtgärdsalternativ som antingen innefattar en nyprövning och anläggandet av fiskvägar, en utrivning av anläggningen eller en effektivisering av befintlig anläggning i samband med en nyprövning. I och med bortledda flöden till fiskväg och minimitappning påverkas anläggningen av ett produktionsbortfall vilket har beräknats för vardera anläggning och berörda åtgärdsalternativ. Produktionsbortfallen som beräknats för exempelfallen är i storleksordningen 2-40 % av anläggningarnas årsproduktion och påverkas främst av om anläggningen har minimitappning eller inte. Vid en effektivisering av befintlig anläggning bör det vid dimensioneringen av turbinen tas hänsyn till volymen på det bortledda flödet till fiskväg och minimitappning för att minimera produktionsbortfallet från detta. Den tid som anläggningen tas ur drift på grund av för låga flöden ökar nämligen när ett flöde leds bort och denna tid kan minimeras.

    Resultaten visar även att de investeringskostnader som kan komma att krävas i samband med en nyprövning är höga sett till anläggningarnas årliga omsättning och risken är därför stor att verksamhetsägare inte kommer ha de ekonomiska förutsättningar som krävs. Detta särskilt i dagsläget då elpriset är lågt och flera av anläggningars elcertifikat nyligen gått ut, vilket innebär minskade marginaler och mindre utrymme för investeringar. Vidare visar fallstudien att en utrivning av anläggning ofta innebär en större kostnad än den för en nyprövning. Det finns alltså en stor risk att de verksamhetsägare som inte har möjlighet att genomföra en nyprövning inte heller kan bekosta den utrivning som de kommer åläggas om nyprövningen inte genomförs. I dessa fall kan en konkurs vara den enda utvägen och det är då oklart vad som sker med anläggningen vilket bör utredas vidare.

  • 179.
    Hagström, Emil
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Grid planning with a large amount of small scale solar power2013Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    With an increasing interest for renewable power, photovoltaics (PV) have becomemore and more common in the distribution network. If a customer wants to install aPV system, or another type of distributed generation (DG), the distribution systemoperators (DSO) needs a good way to determine if it the grid can handle it or not. InSweden, a guideline to aid the DSO was published in 2011. However, this guidelineonly considers one connection without considering other DG units. This project isabout developing new guidelines for DG connections in grids with a large number ofDG units. Based on a literature study it has been concluded that one of the mostcritical issue is over-voltage, which is the main focus of this project.

    Two new methods have been developed; the first proposed method is based onneglecting reactance and losses in the grid, a simple linear relationship between thevoltage level, the resistance in the lines, and the installed power is obtained. Thisrelationship is then used to calculate the voltage level at critical points in the grid. Thesecond method is to find the weakest bus, with a connected DG unit. By assumingthat all power is installed at that point we get a very simple guideline; it is veryconservative but can be used before the first method.

    A simulation tool has been developed in order to analyze the voltage level in grids forvarious cases with connected DG units. The simulated results have proven that theproposed guidelines are, when considering voltage issues, very reliable and can beuseful. However, further work needs to be done to ensure that other problems donot occur.

  • 180.
    Hai, Ling
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Svensson, Olle
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Castellucci, Valeria
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Lejerskog, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Waters, Rafael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Leijon, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Force in the connection line for a wave energy converter: simulation and experimental setup2014Inngår i: 33Rd International Conference On Ocean, Offshore And Arctic Engineering, 2014, Vol 9A: Ocean Renewable Energy, San Francisco, USA, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In order to capture ocean wave energy and transform it into electric energy, Uppsala University has developed a point absorber wave energy converter (AVEC) for electricity production. For a better understanding of a torus shaped buoy's performance, this paper conducts a force analysis under linear conditions, to investigate the hydrodynamic characteristic and line force differences between the torus buoy that is going to be deployed, and two similar cylindrical buoys. The result reveals the line force fromthis torus buoy is roughly 5% larger than from cylindrical buoys for the most energy dense wave climate in Lysekil test site, and negative added mass phenomena won't have a significant impact for the line force. To measure the line force, a force measurement system has been designed. A detailed description is given on the design of the 500 kN force measurement system, and the major differences compared with former force measurement systems. Onshore test result has also been presented. With the force measurement experiment, hydrodynamic analysis for torus buoy can be validated when the system performs linearly, and extreme force for storm weather can be monitored to provide information for future WEC structure's mechanical design.

  • 181.
    Halvarsson, Hampus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Automated Testing of HVDC Control & Protection Systems: A study on Automated Regression Testing2018Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Testing is an important activity when developing a system. Testing requires resources in terms of time, labour and money. By correctly automating the tests, the development time may either be shortened or there will be a possibility to run more tests. ABB in Ludvika has developed MACH, a control & protection system for HVDC (high power electrical transmission over long distances) applications. During development of the control & protection system for each HVDC project, which are all unique, the system is today tested manually, which takes considerable time.This thesis project studies the possibility of automating parts of the MACH system tests, by investigating current testing procedures, the control & protection system itself, and how a test tool may interact with the system. Using this information a test framework, aimed towards test automation, was created, and a simple test execution tool was developed. A new test case, a combination of multiple smaller test cases, ranon the system using the test execution tool.The outcome proves the proof of concept of automating parts of the system tests.The economics and the scope of the automated testing however, is dependent on how automation is implemented.

  • 182.
    Hamrén, Max
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Koch, Martin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Införande av miljözoner i Stockholm: Elbilens påverkan på elnätet2018Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The municipality of Stockholm has released a proposition to battle the increase of pollutants and unwanted noise from transportation in the city of Stockholm. The proposition suggests that Stockholm should implement environmental zones within the city’s tolls. The strategy would promote an electrification of the transportation fleet, starting in year 2020. Currently the proposition includes emissions and noise but disregards the effect from an electrification of the vehicles within the zones. This master thesis investigates the effect an electrified car fleet would have on the electric power grid within the suggested environmental zones. By choosing two local areas in Stockholm electric vehicle charging has been added to the existing power load on the grid in order to evaluate the strain from the vehicle charging. The thesis also investigates the added power consumption based on a complete electrification of the cars within the city tolls. The results indicate that both of the local grids have the capacity to bear the extra load but that the marginal between the power peak and maximum capacity could decrease lifetime expectancy on the power equipment. A complete electrification of all vehicles would mean an 7 % increase of the yearly energy consumption within the tolls.

  • 183.
    Han, Shangfeng
    et al.
    China Univ Petr, Sch Business Adm, Beijing .
    Zhang, Baosheng
    China Univ Petr, Sch Business Adm, Beijing .
    Sun, Xiaoyang
    China Univ Petr, Sch Business Adm, Beijing .
    Han, Song
    China Univ Petr, Sch Business Adm, Beijing .
    Höök, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Naturresurser och hållbar utveckling.
    China's Energy Transition in the Power and Transport Sectors from a Substitution Perspective2017Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 10, nr 5, artikkel-id 600Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Facing heavy air pollution, China needs to transition to a clean and sustainable energy system, especially in the power and transport sectors, which contribute the highest greenhouse gas (GHG) emissions. The core of an energy transition is energy substitution and energy technology improvement. In this paper, we forecast the levelized cost of electricity (LCOE) for power generation in 2030 in China. Cost-emission effectiveness of the substitution between new energy vehicles and conventional vehicles is also calculated in this study. The results indicate that solar photovoltaic (PV) and wind power will be cost comparative in the future. New energy vehicles are more expensive than conventional vehicles due to their higher manufacturer suggested retail price (MSRP). The cost-emission effectiveness of the substitution between new energy vehicles and conventional vehicles would be $96.7/ton or $114.8/ton. Gasoline prices, taxes, and vehicle insurance will be good directions for policy implementation after the ending of subsidies.

  • 184.
    Hansson, Caroline
    SLU, Institutionen för energi och teknik,.
    Analys av skillnader och likheter i EU-länders långsiktiga klimatstrategier2012Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    De internationella klimatförhandlingarna handlar om att hitta lösningar för att stabilisera halten av växthusgaser i atmosfären och att uppnå tvågradersmålet. För att uppnå målet finns olika utsläppsmål att sträva mot. Ett är ett utsläppstak där varje land inte får släppa ut mer än 2 ton CO2-ekv/capita per år för att tvågradersmålet ska uppnås. Ett annat utsläppsmål är att minska de nationella utsläppen med en viss procentsats. EU:s del i minskningen ligger på 80-95 % till 2050.

    Som en del av arbetet mot målet presenterade EU i mars 2011 en färdplan för ett utsläppsnålt samhälle. Där presenteras åtgärder för fem olika sektorer samt hur stora utsläppsminskningarna beräknas kunna vara för varje sektor. Energisektorn är den sektor som beräknas minska mest och väntas nästintill nå en nollnivå. Även bostads- och servicesektorn väntas minska sina utsläpp kraftigt. Jordbrukssektorn är den sektor som beräknas minska minst. I färdplanen uppmanas varje medlemsland att ta fram en nationell färdplan till 2050. Det här examensarbetet syftar till att analysera ett antal av de nationella färdplanerna för att bl.a. ta reda på vilka förutsättningar och möjligheter som har en betydande påverkan.

    Resultatet visar att alla länderna antagit samma mål som EU, nämligen 80 %. Om alla länderna minskar med 80 % till 2050 är det bara Slovenien som når gränsen på 2 ton CO2-ekv/capita. Alla andra länder ligger över gränsen. Vägen till minskade utsläpp är framförallt utsläppsnåla energitekniker, energieffektiviseringar och en ökad användning av el eftersom den har potential att bli emissionsfri. Vindkraft är den teknik som många av de studerade länderna väljer att satsa på, främst till havs då utrymmet på land är begränsat. Kärnkraft är en energikälla som det råder delade meningar om. En del länder anser att det är en bra koldioxidsnål energikälla som gynnar klimatet medan andra länder menar att den är för osäker både ekonomiskt och säkerhetsmässigt. CCS (carbon capture and storage) tas upp av alla de studerade länderna som en möjlig åtgärd för att minska utsläppen. För att minska användningen av fossila bränslen i transportsektorn är det framförallt biodrivmedel och el som ska användas.

    Slutsatser som kan dras av arbetet är att CCS med de rätta förutsättningarna kommer att finnas i större skala 2050 än idag. Elbilar kommer att spela en stor roll i transportsektorn. Kärnkraft och förnybara alternativ är tekniker som kommer att spela en stor roll i energisystemet 2050. För att nå tvågradersmålet krävs internationella överenskommelser som också minskar risken för koldioxidläckage.

  • 185.
    Hansson, Sara
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Naturresurser och hållbar utveckling.
    Approaches to the Bioenergy Potential in 2050: An assessment of bioenergy projections2017Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    There is an abundance of reports and articles on the extent of future bioenergy usage. Decision-makers might turn to bioenergy projections in hopes of making informed decisions for policies or investments. This report aims to highlight irregularities and differences regarding calculations and results in 15 global bioenergy projection studies for the year 2050, and to find underlying connections by applying a metaanalysis with a methodological focus. Statistical distributions were made for the projected global bioenergy potentials. A growth rate study based on the projected global bioenergy potentials was made and used as a simple “reality check”. Regarding Sweden and the EU, it was investigated whether decisions has been made based on estimated bioenergy potentials. The final aim was to make recommendations for bioenergy decision-makers and policy-makers.

    There are many statistical distributions fitting the projections for 2050. The distribution functions showed that with a 95 % confidence level, the bioenergy projections in 2050 is 151.3 EJ. The interquartile range of all studies included in this report for primary bioenergy in the year 2050 was shown to be 120-400 EJ, with minimum value of 30 EJ and maximum of 1600 EJ. A mere third of the projection values were in the vicinity of a linear or exponential trendline based on historical values. The historical annual average growth rate for bioenergy from 1971 to 2011 was found to be 1.9 percent. A higher growth rate is required to achieve the larger quantities that are projected in most studies, the most extreme rate was 7.6 percent, which is far above the average.

    The EU has adopted a biomass action plan partly based on bioenergy projections by the European Energy Agency in 2006. National and international energy projection reports influence Swedish politics, albeit not directly in propositions.

    The difference between individual reports and articles projected bioenergy level in 2050 is significant. It is recommended to read more than one. Most forecasting models and estimates will likely perform poorly numerically, so it is recommended to look for underlying factors, connected longterm trends, or behavioral consequences.

  • 186. Hao, L.
    et al.
    Herrera, D.
    Troi, A.
    The effect of climate change on the future performance of retrofitted historic buildings: A review2018Inngår i: Conference Report: The 3rd International Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström, Lisa Nilsen and Susanna Carlsten, Uppsala University, 2018, s. 60-70Konferansepaper (Fagfellevurdert)
  • 187. Haralambopoulos, Dias
    et al.
    Polatidis, Heracles
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Renewable energy projects: structuring a multi-criteria group decision-making framework2003Inngår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682Artikkel i tidsskrift (Fagfellevurdert)
  • 188. Hatzigeorgiou, Emmanouil
    et al.
    Polatidis, Heracles
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Haralambopoulos, Dias
    CO2 emissions for 1990 – 2020: A decomposition analysis for EU-25 and Greece2010Inngår i: Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, ISSN 1556-7036, E-ISSN 1556-7230Artikkel i tidsskrift (Fagfellevurdert)
  • 189. Hatzigeorgiou, Emmanouil
    et al.
    Polatidis, Heracles
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Haralambopoulos, Dias
    CO2 emissions, GDP and Energy Intensity: A multivariate cointegration and causality analysis for Greece2011Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118Artikkel i tidsskrift (Fagfellevurdert)
  • 190. Hatzigeorgiou, Emmanouil
    et al.
    Polatidis, Heracles
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Haralambopoulos, Dias
    CO2 emissions in Greece for 1990-2002: A decomposition analysis and comparison of results using the Arithmetic Mean Divisia Index and Logarithmic Mean Divisia Index techniques2008Inngår i: Energy, ISSN 0360-5442, E-ISSN 1873-6785Artikkel i tidsskrift (Fagfellevurdert)
  • 191. Hatzigeorgiou, Emmanouil
    et al.
    Polatidis, Heracles
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Haralambopoulos, Dias
    Energy related CO2 emissions for Greece: Decomposition Analysis for 1990-20022008Konferansepaper (Fagfellevurdert)
  • 192. Hatzigeorgiou, Emmanouil
    et al.
    Polatidis, Heracles
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Haralambopoulos, Dias
    Modeling the relationship among Energy demand, CO2 emissions and Economic development: A survey for the case of Greece’2013Inngår i: Global NEST. International Journal, ISSN 1108-4006Artikkel i tidsskrift (Fagfellevurdert)
  • 193.
    Haukka, Astrid
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik, Byggteknik.
    Larsson, Linda
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik, Byggteknik.
    Fasövergångsmaterial för ökad inomhuskomfort: Reducering av temperaturvariationer och kylbehov med hjälp av fasövergångsmaterial2019Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    This report aims to study how the indoor climate in a conference room can be improved by the use of phase change material (PCM). The study includes an experiment where 40 kg of salt hydrate based PCM was placed within a conference room located in an office in the city of Uppsala, Sweden. The experiment resulted in a decrease in the peak temperature with respect to the internal heat gains in the conference room and a slower temperature increase with PCM implemented. The report concludes that PCM can improve the indoor climate in regard to its ability to limit the temperature fluctuation.

    The study also contains modelling and simulation over the office and conference room in the program Trnsys. This was carried out to study how the temperature and cooling demand in the conference room and office respectively would change with a larger implementation of PCM. When 106 kg of PCM was simulated to be implemented in two of the conference room walls, the specific peak temperature was on average decreased with 0.17 °C/kW during the year. Furthermore, a decrease in the cooling demand with 16 % was achieved when implementing 1 208 kg of PCM in the internal walls of the office. This study shows that there is potential for reducing the cooling demand in the building through an implementation of PCM. Further studies with a more detailed model of the office is recommended before deciding upon if and where PCM should be implemented.

  • 194.
    Hedström, Claes
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Kraftvärmeverk som elnätsreglering för laddfordonsladdning2019Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The use of plug-in electric vehicles (PEV) is rapidly growing in many countries. In Sweden the number of PEVs in the transport system grew from about 43 000 in December 2017 to almost 58 000 in July 2018. To fully load a discharged PEV battery in a reasonably brief time will require high charging powers, which might cause high peaks in the power grid. The purpose of this project was to investigate the possibilities for electricity production in combined heat and power (CHP) plants to balance the demand peaks in the power grid caused by charging PEV.

    Data were obtained from different heat production plants in two Swedish cities, Borlänge and Falun. The cities, which have interconnected district heating systems, have a broad spectrum of different types of heat producing plants, and thus functions as an example model of a “typical northern Europe” heating system. An artificial charging load profile was created for a system of a large number of PEVs forming a scalable load. The charging load profile was then used as input in CHP plant models, to generate the heat production profile for the CHP plants in the system. The heat profiles were then used as inputs in a district heating simulation software. The complete Borlänge-Falun heat production system was simulated to find out whether it is possible to operate the CHP plants based on the PEV charging load profile. The generated heat production profiles were similar and clearly followed a pattern that was in line with how the heat and electricity output relate in a CHP plant.

    The results showed that during periods when the heat demand is high, the CHP plants can operate at full load and are thus capable to fully regulate the charging of the PEVs. During periods when the heat demand is low, and the CHP plants are unable to operate on full load, there is a discrepancy between the CHP plants ability to produce electricity and the PEVs charging demand. If the plants are operated at full load even though the heat demand is low, the heat surplus will be lost unless the system is equipped with a large heat storage. This lost heat will lead to increased costs unless there are control means to compensate the CHP plant operator for the peak regulating services as such provided. Furthermore, constructing an energy system were heat is intentionally wasted might not be considered a sustainable solution. The CHP plant regulating system can, however, be combined with other local regulating, e.g. load control, to minimise the heat wasted.

  • 195.
    Hehl, Friedrich
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
    Learning from the Past - Evaluating Forecasts for Canadian Oil Sands Production with Data2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Crude oil plays an important role for the global energy system. As there is ample evidence that conventional oil production will have peaked by 2020, unconventional oil has attained a stronger focus. In particular, oil derived from bitumen from Canadian oilsands has been proposed as a possible remedy to global oil depletion.

    This study aims to test the hypothesis that forecasts on the Canadian oil sands published between about 2000 and 2010 have been overestimating production significantly. A large compilation of oil sands projects, prognoses and production data has been established using openly available databases and reports. Conversion, standardization and analysis of the data was done using the statistical programming language R. The resulting programming code and databases have been compiled into a package available free and open-source online.

    The statistical analysis shows a significant bias of the prognoses towards an overestimation of oil sands production. The compilation shows that most authors tend to overestimate the rate of expansion of the industry. Therefore, any prognosis on the expansion of the industry should be examined thoroughly before use.

  • 196.
    Heikkinen, Piia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    ACCURACY OF THE WEATHER RESEARCH AND FORECASTING (WRF) MODEL IN WIND RESOURCE ASSESSMENT: CASE STUDY ABOUT A POTENTIAL REPOWERING SITE2020Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    This Master’s thesis studies how accurate the Weather Research and Forecasting (WRF) model is in wind resource assessment in the Nordic conditions. Besides, it is studied how big of an increase in energy production could be gained if a confidential wind farm would be repowered. SCADA data from the existing wind farm is filtered and used to calculate the yearly production of the wind farm. WRF data is used as an input in mesoscale-microscale coupling that results in a yearly production estimation for the same wind farm.

     

    When the production results from SCADA and WRF are compared, it is found that the WRF based wind resource assessment overestimates the production with 10 %. This is evaluated to be accurate enough for a preliminary wind resource assessment. This case study confirms that a mesoscale-microscale coupling method where terrain data is combined from two sources leads to acceptable results.

     

    It is also shown that the increase of 26 meters in hub height would increase the annual energy production with 8 % and 51 meters height increase would lead to 15 % more production in case of repowering at the studied site. Compared to the existing wind farm, the only parameter changed was the hub height. Therefore, the results of 8% and 15% should be considered only as indicative estimates. The simplicity and apparent accuracy in the wind resource assessment for a repowering project is though questioned in this study.

  • 197.
    Helander, Emilia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Granskning av möjligheter att påverka effektförlusterna på det svenska stamnätet2017Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The losses on the Swedish national power grid correspond to 2,8 % of the total energy input on the grid and even a small reduction of this can therfore be worth introducing. The purpose of the thesis is to summarise different ways to influence the losses on the Swedish national grid as well as calculating the possible loss reduction from two of these influence possibilities. The study has been requested by the Swidish transmission system operator, Svenska kraftnät. The study is limited to the Swedish power grid with voltages 400 kV and 220 kV. The influence possibilities exclude anything that demand physical changes to be made on the power grid. The study is mostly based on interviews with people that have insight in the isssue, ss well as a study on relevant literature.

    The result show that there are seven different possible ways to reduce the losses on the power grid. What extent of measures that is necessary for instating these loss reductions varies, but thay arr described in the study. Calculations on two of these loss influences where made and showed that a loss reduction of around 740 MWh/year can be achieved from optimizing the usage of power transformers on the grid. Furthermore, other calculations show that if the maintenance method, live work, had been used for the past ten years, losses could have been decreased by approximately 58 800 MWh. This shows that the possible loss reduction can vary a lot depending on which method you use.

  • 198.
    Helander, Hanna
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Larsson, Lovisa
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Emissions and Energy Use Efficiency of Household Biochar Production during Cooking in Kenya2014Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    This project examines the efficiency of a biochar-producing stove in meeting the needs of households in rural of Kenya. The stove has been tested and evaluated by five household in Embu, Kenya and compared with two other common cooking methods. The main parameters were time consumption, fuel consumption and emissions of carbon monoxide and particulate matter. Usability and energy use efficiency have also been evaluated. Three potential feedstocks have been examined for use in the biochar-producing stove; Grevillea prunings, maize cobs and coconut husks.

    The biochar-producing stove was well received by the households. It has potential of saving time, it saves fuel and it has a significantly lower level of emissions than other examined stoves. Despite some challenges related to the usability and the handling of the stove, an implementation of the biochar-producing stove can contribute to an alleviation of the women’s burdens, save fuel and contribute to a healthier indoor air climate. 

  • 199.
    Hellesen, Carl
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Wolniewicz, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Jansson, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Håkansson, Ane
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Jacobsson Svärd, Staffan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Österlund, Michael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Transient Simulation of Gas Bubble in a Medium Sized Lead Cooled Fast Reactor2014Inngår i: Proceedings of the International Conference on Physics of Reactors (PHYSOR 2014) / [ed] Kenya Suyama, Takanori Sugawara, Kenichi Tada, Go Chiba and Akio Yamamoto, 2014Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    A common problem for many liquid metal cooled fast reactor designs is the positive void worth of the coolant. In this context, an advantage of lead cooled fast reactors is the high temperature of coolant boiling. In contrast to sodium cooled fast reactors this, in practice, precludes coolant boiling. However, partial voiding of the core could result from e.g. gas bubbles entering the core from below. This would introduce a positive reactivity, if the bubble is large enough.

     

    In this paper we model this type of event using a point kinetics code coupled to a heat transport code. The reactivity parameters are obtained from a Monte Carlo code. The 300 MWth reactor design Alfred is used as a test case. We show that in general the reactor design studied is robust in such events, and we conclude that small bubbles a measureable Power oscillation would occur. For very large bubbles there exist a possibility of core damage. The cladding is the most sensitive part.

  • 200.
    Hellström, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Development of a model for estimation of wind farm production losses due to icing2013Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Wind turbines operating in cold climate are exposed to periods of icing which lowers the plantprofitability by affecting the annual production. The loss of production has two components:The first (and most important) component is reduced power during operation due to disturbedaerodynamic properties of the blades. The second component is increased standstill.

    During this thesis project, methods to estimate production losses of a wind farm due to icinghave been developed, as well as a software tool to facilitate the use of these methods and thepresentation of the results. A method based on common metrological data and availableproduction data was desired, as modelling ice-related losses is expensive and may be inaccurate.

    The methods developed are based on using measured data for each turbine, such as activepower, temperature, wind direction and wind speed, and through this data describe theindividual turbine’s performance during different conditions. Production losses were thenestimated by comparing actual and expected power output (for the given wind speed). Thethesis then expanded on this basic concept by using reanalysis and mesoscale modelled data,which offers greater variety in the way estimating the losses may be performed, as well as theoption to derive losses for periods not covered by the production data.

    It was also important to develop a flexible and portable method that could incorporate newseasons of data or estimate losses for different wind farms with a completely differentconfiguration of turbines.

    The methods are developed using data from a wind farm in northern Sweden, consisting of 40Vestas V90 turbines and constructed a few years ago.

    It was found that eastern position in the wind farm and turbine altitude correlates with higherice-related losses, and that easterly winds relate to higher such losses than westerly winds. Thelosses during operation were estimated to 6.4 % of annual possible production and stops due toicing to 2.1 % of the total time. The losses figures are comparable to an earlier study performedin 2011 based on the same wind farm.

    The possibility of anti- or deicing systems for the wind farm and the profitability of such aninvestment should be further investigated as the wind farm is expected to continue operation fortwenty years or more.

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